       (aset obj key rea))
     res))
 
+(defn check-derefs [f]
+  (let [ctx (js-obj)
+        res (in-context ctx f)]
+    [res (some? (.-captured ctx))]))
+
 
 ;;; wrap
 

                 false))))))

(defn- in-context [obj f]
  (set! (.-cljsCapPos obj) 0)
  (binding [*ratom-context* obj]
    (f)))

(defn- deref-capture [f obj]
  (let [watch (.-watching obj)]
    (set! (.-cljsCaptured obj) (.-watching obj))
    (when (dev?)
      (set! (.-ratomGeneration obj)
            (set! generation (inc generation))))
    (let [res (in-context obj f)
          capt (.-cljsCaptured obj)]
      (set! (.-cljsCaptured obj) nil)
      (set! (.-dirty? obj) false)
      (when-not (arr-eq capt watch)
        (._update-watching obj capt))
      res)))

(defn check-derefs [f]
  (let [ctx (js-obj)
        res (in-context ctx f)]
    [res (some? (.-cljsCaptured ctx))]))

(defn- add-item [a x]
  (when (== -1 (.indexOf a x))


(defn- notify-deref-watcher! [derefable]
  (when-some [obj *ratom-context*]
    (let [c (.-captured obj)]
      (if (nil? c)
        (do (set! (.-capPos obj) -1)
            (set! (.-captured obj) (array derefable)))
        ;; Try to avoid allocating new array
        (let [p (.-capPos obj)]
          (if (== p -1)
            (add-item c derefable)
            (if (identical? derefable (aget c p))
              (set! (.-capPos obj) (inc p))
              (let [c1 (set! (.-captured obj) (.slice c 0 p))]
                (add-item c1 derefable)
                (set! (.-capPos obj) -1)))))))))

(defn- check-watches [old new]
  (when debug
